The present invention relates to ribbon cartridges and especially to a cartridge for an endless inked ribbon for printing mechanisms for use with computer terminals and the like. This patent is an improvement to the assignees patent application for Endless Inked Ribbon Cartridge, Ser. No. 622,223, now U.S. Pat. No. 3,993,182 which was an improvement to the assignees patent for Endless Printer Ribbon Cartridge Apparatus, U.S. Pat. No. 3,918,569.
In the past a great many manufacturers have provided ribbon cartridges for use with their typewriters or printing mechanisms to replace the individually wrapped ribbons which must be individually threaded to the typewriter from a ribbon wrapped upon a spool to an empty spool. This in turn results in the operator's hands becoming smudged or messy during the replacement of a ribbon. Cartridge ribbons, on the other hand, may be connected from the wound spool to an empty spool and may be snapped in place with a minimum of inconvenience and time lost. A typical cartridge ribbon may operate with a preinked ribbon as well as with carbon ribbons which are destroyed once used or with ribbons that are continueously inked during the operation.
Typical prior art ribbon cartridges for typewriters or printer mechanisms may be seen in U.S. Pat. No. 3,621,968 for a ribbon cartridge with mobius loop in the ribbon which utilizes an endless ribbon through a serpentine path within a cartridge and uses a mobius loop configuration to effectively double the length of the ribbon and includes an ink pad mounted in contact with the ribbon for continueously inking the ribbon. A similar endless ribbon feeding mechanism may be seen in U.S. Pat. No. 3,755,905 in which an endless ribbon feeding device is adapted for shorthand typewriters and in U.S. Pat. No. 3,685,357 an endless ribbon feeding mechanism for typewriters is randomly looped inside a casing and fed out of the opposite end of the casing. Typewriter ribbon cartridges are also utilized for feeding from a full to an empty spool, such as illustrated in U.S. Pat. No. 3,731,781 for a Ribbon Supply Cartridge. Endless ribbon cartridges may also be seen in U.S. Pat. No. 3,726,381 and in U.S. Pat. No. 3,728,963. In addition, there have been cartridge feeding mechanisms utilized for prerecorded magnetic tapes feeding spools of plastic ribbon coated with an iron oxide or similar material past magnetic record and playback heads.
The present invention is an improvement over a previous endless printer ribbon cartridge apparatus and provides special compensation for the wide latitudes in ribbon length which results from tension stresses induced in slitting, inking or winding operations and which typically may be caused by pre-winding tension stresses or an elongation due to continual character impact.